Method and apparatus for controlling noise producing equipment

ABSTRACT

Method and apparatus for controlling noise producing equipment is disclosed. The equipment may include a rotor having a plurality of cutting edges projecting therefrom which coact with a stationary bed knife to comminute plastics material. The upper surface of the bed knife constitutes an approaching surface for the cutting edges of the rotor while the lower surface of the bed knife defines a receding surface for these same elements. Suction means provide a zone of reduced pressure proximate to the approaching surface of the bed knife and the rotor with its cutting edges to reduce the level of noise during operation of the equipment. Alternatively, means are included to apply a zone of increased fluid pressure proximate to the receding surface of the bed knife and the rotor with its cutting edges simultaneously with the application of the reduced pressure as aforesaid to effect said noise reduction.

United States Patent 1191 Shah 1451 Sept. 30, 1975 METHOD AND APPARATUS FOR CONTROLLING NOISE PRODUCING [73] Assignee: Cumberland Engineering Company,

Inc., Pawtucket, R.l.

[22] Filed: Feb. 20, 1974 Appl. No.: 444,248

[52] U.S. Cl. 83/169; 831/3563; 83/70l;-

' I 181/33 B [51] Int. Cl. B26D 7/00 [58} Field of Search 83/22, 24, 98, 99, 100, 83/169, 355, 356.3, 701; 181/33 B, 33 C [56] References Cited UNITED STATES PATENTS 2,347,046 4/1944 Geiger 83/100 x 2,768,689 10/1956 Ewing 83/355 x 3,228,274 l/l966 Cagen 83/355 x 3,651,726 3/1972 Larochel. 83/355 X 3,762,256 10/1973 Frantz 83/356.3 Lowen et al. 83/356.3 X

' Primary Examiner-l M. Meister Attorney, Agent, or FirmB. W. Norton [5 7 ABSTRACT Method and apparatus for controlling noise producingequipment is' disclosed. The equipment may include a rotor having a plurality of cutting edges projecting therefrom which coact with a stationary bed knife to comminute plastics material. The upper surface of the bed knife constitutes an approaching surface for the cutting edges of the rotor while the lower surface of the bed knife defines a receding surface for these same elements. Suction means provide a zone of reduced pressure proximate to the approaching surface of the bed knife and the rotor with its cutting edges to reduce the level of noise during operation of the equipment. Alternatively, means are included to apply a zone of increased fluid pressure proximate to the re ceding surface of the bed knife and the rotor with its cutting edges simultaneously with the application of thereduced pressure as aforesaid to effect said noise reduction.

14 Claims, 5 Drawing Figures US. Patent Se t. 30,1975 sheet 1 OH 3,908,497

US. Patent Sept. 30,1975 Sheet 2 of4 3,908,497

I00 IOO DBA WITHOUT SUCTION (AT BEHIND DISCHAEV/ 90 9Q {(W|TH SUCTION) 80 so F I 3 1r T '60 60 E u so 50 T O 7 Q 3 40 40 LU 2 \VACUUM FLOW (CFM) 2 3 S 200 400 600 800 I000 I200 I400 I600 ROTOR SPEED RPM US. Patent Sept. 30,1975 Sheet 3 of4 3,908,497

US. Patent Sept. 30,1975 Sheet 4 of4 3,908,497

METHOD AND APPARATUS FOR CONTROLLING NOISE PRODUCING EQUIPMENT BACKGROUND OF THE INVENTION The present invention relates to method and apparatus for the controlled operation of potentially noisy equipment and relates, more particularly, to controlling the noise level output of said equipment.

It has long been desired to operate potentially noisy equipment having relatively moving parts so that the noise level output therefrom could be reduced to an absolute minimum. Modern day industrial laws have imposed a strict mandate in this regard. Thus, presently there exists the requirement that noise levels in industrial environments be reduced to acceptable tolerances in order that operators of such equipment can tend them for sustained periods of time. To this end it has been necessary heretofore to resort to such practices as operating equipment at lower speeds, encasing the equipment in sound-proof enclosures, reducing the duration which the operators are exposed to the noisy equipment, and restricting the number of such noisy pieces of equipment that can be present in a single operating area. Obviously, such practices are quite expensive and, in some cases, are of limited practical value.

SUMMARY OF THE INVENTION The present invention is directed to apparatus wherein a movable means, such as a materials cutting rotor, is caused to move past a second means, such as a stationary bed knife cooperable with the rotor, in a manner to disturb the atmosphere in the region of the rotor and bed knife and thereby produce noise having a fundamental frequency proportional to the rate of rotation of the rotor relative to the bed knife. Such noise, produced by disturbance of the atmosphere is to be distinguished from noise produced by solid-to-solid impact. While the applicant is not bound to any theory in the operation of his invention, it has been theorized that the noise produced by the movement of each of the rotor knives past the bed knife results from the movement of the boundary layer of air surrounding the rotor at a high velocity toward the bed knife, and then the sudden reduction of the velocity of this air column to essentially zero as each rotor knife in turn moves past the bed knife. This sets up vibrations in the boundary layer of air surrounding the rotor which leads to the resultant noise, the level of noise producedbeing a function of the number of rotor knives and the angular speed of the rotor. By destroying this boundary layer of air about the rotor, or at least most of it, by the application of a reduced pressure in the zone where the rotor knives approach the bed knife, or, alternatively, by a combination of this reduced pressure with an increased pressure in the zone on the opposite side of the bed knife, the aforementioned vibrations in the air column are dissipated. Consequently, the noise level is reduced.

One object of the present invention is to provide method and apparatus for substantially reducing the noise level in noise producing equipment of the kind wherein a movable member is caused to coact with a second member to disturb the atmosphere and produce noise.

A further object of the invention is to provide method and apparatus for producing a zone of reduced pressure proximate to coacting movable and stationary members which are potentially noisy as a result of their coaction disturbing the atmosphere so as to reduce the level of the noise produced thereby.

Still another object of the present invention is -to provide method and apparatus for producing opposing zones of increased and reduced pressure proximate to coacting movable and stationary members which are potentially noisy as a result of their coaction disturbing the atmosphere so as to reduce the level of noise produced thereby.

Other objects of the invention will in part be obvious and will in part appear hereinafter. A

BRIEF DESCRIPTION OF THE DRAWING Reference is now made to the accompanying drawing wherein:

FIG. 1 is a cross-sectional view of a plastics cutting machine known as a pelletizer incorporating the present invention;

FIG. 2 is a front elevational view taken along lines II-II of FIG. 1;

FIG. 3 is a graph showing comparative results in the levels of noise produced in practice with the present invention when employed with equipment of the type illustrated in FIG. 1 and in the absence of said invention.

FIG. 4 is a view similar to FIG. 1 illustrating an alternate embodiment of the invention; and

FIGS. 5 and 6 are detail views showing blade arrangements used in dicing machines.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has already been stated that a principal application of the invention is to machines of the kind in which a stationary bed knife is employed and a rotor having a plurality of cutting I edges projecting therefrom is brought into cooperative relationship with the cutting edge of the bed knife by rotation of the rotor,and especially where the cutting edges of the rotorand/or the cutting edge of the bed knife reside generally parallel or inclined with the rotational axis of the rotor. Machines with knife, edge arrangements of the type just described are used for comminuting plastics materials to sizes suitable for use as raw material in extrusion or injection moldingmachines. One example of such a machine as just described is the Cumberland Model 6" Pelletizing Machine manufactured and sold by Cumberland Engineering Company, Inc., South Attleboro, Mass. Such pelletizer has a single stationary cutting blade with a linear cutting edge and the cutting edges mounted in the companion rotor are also linear, i.e., straight-edged. In use, the pelletizer is fed with extruded lengths of plastics material which usually are of circular, rectangular or oval cross section. The machine operates to cut the lengths into short pellets. A number of such lengths are normally fed into the machine in side-by-side relationship to make full use of the entire length of the cutting edges of the bed knife and companion rotor.

Turning now to FIG. 1 a pelletizer of the type generally described above is exemplified and here the pelletizer 10 is seen to include a generally cylindrical rotor 12 which is substantially enclosed with a sheet steelhousing 14. The housing 14, in turn, is affixed to a bed 16 supported from a frame 18 extending to the floor. Rotor 12 is provided with a plurality of straight-edged cutting edges or knives 20 say, twenty-four in number,

. 0f the knives is secured to a suitable step 26 by means of a plurality of bolts 28. Rotation of rotor 12 is accomplished by energizing a variable speed electric motor 30,'the power being transmitted therefrom to rotor 12 via belt 32.

As rotor 12 is driven in the direction of arrow 34 the cutting edge of each knife in turn is brought into close cutting relationship with the linear cutting edge 40 formed in the upper surface 41 ofa stationary bed knife 42 secured to bed knife block 43. The spacing between the cutting edge of each rotor knife 20 at its closest point of approach to bed knife cutting edge 40 is approximately 0.00l 0.002 inches. As best seen in FIG. 2 bed knife 42 is generally coextensive in length with the length of rotor 12 and its knives 20. Further, bed knife 42 and its cutting edge 40 are parallel to the rotational axis of rotor 12. For purposes of this discussion the area bounded by cutting edge 40 and the upper surface 41 and extending upwardly therefrom may be considered an approaching zone with respect to rotor knives 20 while the area bounded by cutting edge 40 and extending therebelow may be deemed a receding zone for these same knives.

Feed rolls 50 and 52 are provided to feed the extruded plastic strip stock (not shown) in the direction of arrow 54 across the upper surface 41 of bed knife 42 to be cut into pellets by the coaction of the cutting edges of knives 20 and bed knife 42. After cutting, the pellets are flung downwardly by rotor 12 through throat 58 in bed 16 for suitable collection.

To this point the description has been generally confined to a pelletizer of known construction and only so much of the structure of that pelletizer has been set forth herein as is deemed necessary to a full and complete understanding of the present invention.

With attention once again to FIG. 1 the present invention includes a suction nozzle 70 connected via suction hose 72 to the intake side 73 of a blower 74 secured to bed 16. Nozzle 70 is affixed in position by means of a bracket 76 which is fastened to the top surface 78 of housing 14 by bolts 80 so that the nozzle is adjustable horizontally toward and away from cutting circle 22 of rotor 12. A further bracket 84 is employed to permit vertical adjustment of nozzle 70 relative to bed knife 42. Nozzle 70 is provided with an elongated delivery aperture 86 which is coextensive with the axial length of rotor 12 and the length of knives 20, as best seen in FIG. 2. Also as seen in FIG. 2 the major dimension of aperture 86 is parallel with the rotational axis of rotor 12. Suction pump 74 is driven via a belt 88 from motor 30 and. in consequence thereof, a suction, i.e., a zone of reduced pressure, is created proximate to the upper surface 56 of bed knife 42 and the area where the rotor knives 20 approach or converge with said upper bed knife surface. By virtue thereof, the

level of noise produced by the pelletizer during its op correct vacuum pressure is supplied automatically as correlated with the rotational speed of rotor 12.

In FIG. 3 a graph is illustrated presenting the noise reduction achieved with the employment of suction applied in the zone bounded by the upper surface 41 of bed knife 42 of a pelletizer and the cutting circle 22 of the rotor knives. In this experiment baffling was provided from slightly above the uppermost region of the cutting circle 22 upwardly to the interior upper surface 90 of housing 14 to restrict the pellets being produced from entering the suction orifice. The rotor utilized in deriving the results shown in FIG. 3 was eight inches in diameter and was provided with eight equidistantly spaced knives. The suction was provided by a one inch diameter orifice positioned 4% inches upwardly from cutting edge 40 of bed knife 42. During the derivation of the date exhibited in FIG. 3 the pelletizer was not pelletizing any materials. It is seen from FIG. 3 that the present invention admits of substantial noise reduction in an environment where potentially noisy machine is employed which disturbs the atmosphere. Obviously, the data presented in FIG. 3 is representative of simply one set of conditions and is presented by way of example only. Noisy reduction results for any given set of conditions when the present invention is used will depend on particular operating conditions.

FIG. 4 there is shown a modification of the present invention wherein there is combined with the aforedescribed reduced pressure technique an increased fluid pressure such as air which is presented in the zone bounded by the cutting circle 12 and below cutting edge 40 of bed knife 42, i.e., that area where knives 70 recede from bed knife 42. Thus, a nozzle of substantially the same configuration as nozzle 70 and having an elongated delivery aperture 102 is connected to the discharge side 104 of blower 74 via hose 106. Obviously a separate blower could be provided for each of the nozzles 70 and 100, if desired, and it is equally obvious that each pump could be powered by a source independent of drive motor, if desired. Aperture 102 is desirably of a width coextensive with the axial length of rotor 12 and blades 20 and the major length of the aperture is parallel with the rotational axis of rotor 12. Nozzle 100 is secured to bed 16 by means of a bracket which has bolts 112 and 114 slidable in respective elongated slots (not shown) to thereby permit vertical and horizontal adjustment of the nozzle. In operation, as motor 30 is powered to drive rotor 12 air pump 74 is similarly driven to provide pressurized air to the region or receding zone below cutting edge 40 and proximate to rotor 12 while suction is simultaneously applied to the approaching zone above the cutting edge and proximate to the rotor.

A dicing machine for reducing plastic sheet stock to small pieces of generally uniform size and shape may be provided in similar form to the machine of FIG. 1, but with a modified blade arrangement. The arrangement of FIG. 5 uses a stationary bed knife 42' with a straight cutting edge 40' and castellated blades 120, 122 on the rotor, the castellations of any one blade being staggered with respect to those on either side thereof. The arrangement of FIG. 6 shows a portion of a ratchet tooth dicer where the bed knife 42" and the blades 124, 126 of the rotor are serrated. In this arrangement the rotor blades are operable to traverse only through alternate spaces of the bed knife 42" at any one time. The serrations shown in FIG. 6 are asymmetric. In another arrangement of a dicing machine known as a stair step dicer the serrations are bounded by edges equally and oppositely inclined to the lengths of the knives and are substantially perpendicular to one another. A stair step dicer produces pieces which are more nearly cuboidal than does a ratchet tooth dicer, but requires the feed-stock to be fed in a direction inclined, usually at 45, to the axis of the rotor. Arranging an air nozzle after the manner described with reference to either EIG. 1 or FIG. 4 effectively diminishes the disturbance noise produced by a dicing machine during cutting the sheet stock.

It will be understood that the foregoing description of the effects obtainable by the application of the invention to pelletizers and dicing machines is given by way of illustration only. Other applications of the invention will be apparent to those skilled in the art. Thus, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative only and not in a limiting sense.

I claim:

1. Apparatus comprising, movable means, second means arranged in close proximity to said movable means, said movable means and said second means coacting to disturb the atmosphere and produce noise, said second means defining an approaching zone for said movable means and a receding zone for said movable means, and suction means operable to produce a reduced pressure proximate said movable means and said approaching zone, said reduced pressure being less than the pressure in said receding zone, to thereby reduce the level of said noise. I

2. Apparatus as set forth in claim 1 wherein said movable means is rotary means, and said second means is non-rotating means.

3. Apparatus as set forth in claim 1 including advancing means for presenting material to said movable means and said second means for treatment thereby.

4. Apparatus as set forth in claim 2 including means operable to direct a positive pressure proximate to said receding zone and said rotary means.

5. Apparatus as set forth in claim 2 wherein said rotary means is a rotor having a plurality of cutting edges therein, and the noise produced is a function of the number of said cutting edges and the rotational rate of said rotary means.

6. Apparatus as set forth in claim 4 wherein said means for producing said positive pressure includes a nozzle having aperture means the major dimension of which is generally coextensive with the length of said cutting edges.

7. Apparatus as set forth in claim 4 wherein said suction means and said positive pressure means are connected to common generating means for inducing suction in said suction means and emitting positive pressure through said increased pressure means.

8. Apparatus as set forth in claim 5 wherein said rotor rotates about an axis and said cutting edges are arranged generally parallel with said axis.

9. Apparatus as set forth in claim 5 wherein said rotor comprises a generally cylindrical member and said cutting edges project from said member.

10. Apparatus as set forth in claim 5 wherein said non-rotating means is a stationary member having a straight cutting edge thereon, and the cutting edges of said rotor are straight.

11. Apparatus as set forth in claim 5 wherein said non-rotating means is a stationary member having a straight cutting edge thereon, and the cutting edges of said rotor are serrated.

12. Apparatus as set forth in claim 5 wherein said nonrotating means is a stationary member having serrated cutting edges thereon, the cutting edges of said rotor being serrated and being positioned to be brought into cooperative relationship with said cutting edges of said stationary member during rotation of said rotor.

13. Apparatus as set forth in claim 5 wherein said suction means includes a nozzle having aperture means the major dimension of which is generally coextensive with the length of said cutting edges.

14. Apparatus as set forth in claim 5 wherein said rotor rotates about an axis and said cutting edges are inclined with respect to said axis.

=l l l= 

1. Apparatus comprising, movable means, second means arranged in close proximity to said movable means, said movable means and said second means coacting to disturb the atmosphere and produce noise, said second means defining an approaching zone for said movable means and a receding zone for said movable means, and suction means operable to produce a reduced pressure proximate said movable means and said approaching zone, said reduced pressure being less than the pressure in said receding zone, to thereby reduce the level of said noise.
 2. Apparatus as set forth in claim 1 wherein said movable means is rotary means, and said second means is non-rotating means.
 3. Apparatus as set forth in claim 1 including advancing means for presenting material to said movable means and said second means for treatment thereby.
 4. Apparatus as set forth in claim 2 including means operable to direct a positive pressure proximate to said receding zone and said rotary means.
 5. Apparatus as set forth in claim 2 wherein said rotary means is a rotor having a plurality of cutting edges therein, and the noise produced is a function of the number of said cutting edges and the rotational rate of said rotary means.
 6. Apparatus as set forth in claim 4 wherein said means for producing said positive pressure includes a nozzle having aperture means the major dimension of which is generally coextensive with the length of said cutting edges.
 7. Apparatus as set forth in claim 4 wherein said suction means and said positive pressure means are connected to common generating means for inducing suction in said suction means and emitting positive pressure through said increased pressure means.
 8. Apparatus as set forth in claim 5 wherein said rotor rotates about an axis and said cutting edges are arranged generally parallel with said axis.
 9. Apparatus as set forth in claim 5 wherein said rotor comprises a generally cylindrical member and said cutting edges project from said member.
 10. Apparatus as set forth in claim 5 wherein said non-rotating means is a stationary member having a straight cutting edge thereon, and the cutting edges of said rotor are straight.
 11. Apparatus as set forth in claim 5 wherein said non-rotating means is a stationary member having a straight cutting edge thereon, and the cutting edges of said rotor are serrated.
 12. Apparatus as set forth in claim 5 wherein said non-rotating means is a stationary member having serrated cutting edges thereon, the cutting edges of said rotor being serrated and being positioned to be brought into cooperative relationship with said cutting edges of said stationary member during rotation of said rotor.
 13. Apparatus as set forth in claim 5 wherein said suction means includes a nozzle having aperture means the major dimension of which is generally coextensive with the length of said cutting edges.
 14. Apparatus as set forth in claim 5 wherein said rotor rotates about an axis and said cutting edges are inclined with respect to said axis. 